Dynamic Response Of Utility Tunnel Under Gas Explosion

With the rapid spread and development of the clean natural gas,there are a growing number of gas explosions in the world.Gas explosions not only bring economic and personal casualties,but also may cause partial damage or even overall destruction and collapse of the building.As a new underground building in the city,the underground pipe gallery is mainly used to centralize various types of municipal pipelines,yet becomes an important guarantee for the people’s convenience.In this paper,against the engineering background of city’s integrated and assembled pipe gallery,ANSYS/LS-DYNA finite element software is used to establish the dynamic analysis of the model of the integrated pipe gallery under the gas explosion load based on the fluid-structure interaction algorithm.And the results are as follows:(1)Establish six gas explosion models of different volumes of methane-air mixture gas in the underground pipe gallery,analyze the air unit in each working condition,extract the air overpressure time history curve of each working condition and analysis overpressure peak value of the air unit,obtain a mathematical analytic formula of the pressure peak curve of air shock wave that are different distances from the gas surface under the same gas volume.Statistic and fit the pressure peak curve of air shock wave at different distances from the gas surface under six working conditions,then get the mathematical analytic formula of the pressure peak curved surface of air shock wave at different gas volumes and different distances from the gas surface.(2)Establish a model of the integrated underground pipe gallery,calculate the methane’detonation shock wave and air shock wave in the gas explosion under the three different concentrations of methane,and verify that the 9.5% methane gas concentration is the gas explosion’s "best" theoretical concentration.Focus on the dynamic response of the reinforced concrete pipe’s internal measuring points,external measuring points and main steel measuringpoints when gas explosion occurs in integral reinforced concrete pipe gallery at this concentration,including the concrete stress time-history curve and the steel bar force time-history curve.Used the formula of peak surface of fitting air shock wave,calculated the pressure peak of air shock wave at the top slab,side wall and bottom slab,and applied dynamic load curve on the inner side of the pipe corridor for numerical simulation.At the same time,compare the results of fluid-structure interaction algorithm.And the node displacement time history curve.Although the integrated pipe gallery is subjected to large impact loads under gas explosion load,because its good integrity does not cause obvious structural and collapse damage of the pipe gallery,but it is still necessary to strengthen the anti-flammability of pipe gallery during design.(3)A model of the assembled underground pipe gallery was established,and the prestressed steel bar was prestressed by a cooling method,and a gas explosion occurred at a concentration of 9.5% methane gas.By collecting and analyzing the displacement time history curve of the concrete joint at the joint of the assembled pipe gallery and the axial force and axial stress time history curve of the prestressed steel bar,the gas explosion load is the main factor for increasing tensile stress of steel bar that at joint of the assembled pipe gallery.When considering the blasting load,it is necessary to appropriately increase the amount of reinforcement of the prestressed steel bar,and at the same time strengthen the shock resistance of the prestressed steel bar.